RO membranes

[StirCrazy]

Originally Posted by reefermadness

NO he mentioned the PRV as something someone could adjust to get your house plumbing at a higher PSI. The PRV is located near you main shut off I guess (still havent went looking for mine). .

ah, ok.. I never had one in my houses. I had to install one in the first house as they jacket the PSI, but my PSI in the second house sucked so I had to buy a booster pump.

Originally Posted by reefermadness

As for the GPD ratings being multiple on Dow membranes, when I look at the dow filmtec membranes are not sold like this. I believe that virtually any ro membrane will produce more GPD when higher pressure is applied. The problems with doing so is that the rejection rating will be affected. If you want rejection ratings similar (I actually find them better) then advertised then you should run them to spec.

DOW never sold them this way, it was a company who was buying dow mwmbrains and relabling them as so many GPD@60PSI and so many @ 90 PSI. the rejections rates are constant through out there operating range as Dow is giving a minimum operating spec. I installed several systems over the last 8 years (comercial and non comercial) so I have had to talk to DOW directly on a few of the aplications and what I got from there engineers was that the rejection rate won't change untill the membrain starts to break down. so if you operate it in a way the is dammaging then you will get degraded preformance. operating at 100 PSI wont cause this, operating at 150 might start to as that is its upper end. at any rate I was confadent running my own at 120 PSI with a high volume pump to suply the water (only had 40 PSI at the second house) so after two years the output was still "0".

Steve

[reefermadness]

Well I have to ask then. If all it takes is more pressure applied to the 75gpd membrane and it will produce 150gpd with the same rejection rating then what is the difference between the two membranes??

[StirCrazy]

Originally Posted by reefermadness

Well I have to ask then. If all it takes is more pressure applied to the 75gpd membrane and it will produce 150gpd with the same rejection rating then what is the difference between the two membranes??

the amount they will put out at the industry standard of 50PSI.

Steve

[reefermadness]

The dow filmtec 150gpd is spec'd at 65psi input. Anything less and you will not get 150gpd.

Take a look at the specs sheet posted at BRS. I will attempt to post it here but don't know if it will like hot linking.

[StirCrazy]

um, DOW doesn't make a 150, they also don't make membrains that the part number starts with TF. the DOW membrains that most of us use are
TW30-1812-GPD (24,36,50,75,and 100)

so you have managed to show a info sheet for a non dow product.

Steve

[Doug]

You guys have made this a thread full of info. Good reference for the future.
My new restrictors came in today. Going to pull the bypass and install one in the line. Guess I will just have to put the bypass in to use. At least until I use up this membrane.

[StirCrazy]

Originally Posted by Doug

You guys have made this a thread full of info. Good reference for the future.
My new restrictors came in today. Going to pull the bypass and install one in the line. Guess I will just have to put the bypass in to use. At least until I use up this membrane.

Bah, no one will see this in the future, if they would, they would have found the threads from 8 or 9 years ago with all the same info

Steve

[reefermadness]

Originally Posted by StirCrazy

um, DOW doesn't make a 150, they also don't make membrains that the part number starts with TF. the DOW membrains that most of us use are
TW30-1812-GPD (24,36,50,75,and 100)

so you have managed to show a info sheet for a non dow product.

Steve

Apparently I did. I didnt realize that the 100gpd and 150gpd membranes that BRS sells are not dow filmtec. I got that spec sheet from their website.

How ever my understanding still is that all membranes must be used at the spec pressure to achieve the best rejection rate. You can up the pressure but you will see a decrease in the rejection rating.

You are right that all dow membranes are spec at 50psi. The 100gpd has a poorer rejection rating though, and they don't make a 150gpd.

[StirCrazy]

Originally Posted by reefermadness

Apparently I did. I didnt realize that the 100gpd and 150gpd membranes that BRS sells are not dow filmtec. I got that spec sheet from their website.

How ever my understanding still is that all membranes must be used at the spec pressure to achieve the best rejection rate. You can up the pressure but you will see a decrease in the rejection rating.

You are right that all dow membranes are spec at 50psi. The 100gpd has a poorer rejection rating though, and they don't make a 150gpd.

there may be a slight decrease in rejection rating, but it is not one that would be measurable and definatly not enough to be worried about.

we routeenly installed systems which were intended to make drinking water from untreated water and we would set them up at 100PSI. send in water samples and they would come back just as good as the plaves that have lower pressure. We also checked with DOW engineers befor setting them up this way. what we were led to believe is even at the max operating PSI of 150, the DOW filmtec would still have a better rejection rate than other brands. now this was about 8 years ago so who knows the quality of the copy brands now.

Now from running my own RO, at 50 PSI I get 0 PPM out, at 125 PSI, I get 0 ppm out. now that was with between 20 to 60 PPM in (depends on time of season)

Steve